Line feed mechanism for string trimmer

Patent metadata

Field	Value
Publication number	US-2016143218-A1
Application number	US-201414552682-A
Country	US
Kind code	A1
Filing date	Nov 25, 2014
Priority date	Nov 25, 2014
Publication date	May 26, 2016
Grant date	—

Abstract

A string trimmer with a controller that brakes an electric motor so that the electric motor can selectively generate a moment that is used as a control signal for a line pay-out mechanism.

First claim

What is claimed is:

1 . A string trimmer comprising:
an electric motor; a rotatable output member driven by the electric motor; a handle coupled to the electric motor; a spool assembly that is adapted to hold a trimming line such that the trimming line has one or more line segments that extend from the spool assembly, the spool assembly having a spool housing, a spool and a line pay-out mechanism, the spool being driven by the output member and configured such that the trimming line is wound thereon, the line pay-out mechanism being configured to control rotation of the spool relative to the output member; and a controller coupled to the electric motor and configured to selectively brake the electric motor, wherein electrical braking of the motor causes the line pay-out mechanism to operate in a pay-out mode to permit the spool to rotate relative to the output member to pay-out trimming line.

2 . The string trimmer of claim 1 , wherein the electric motor is housed in a powerhead assembly.

3 . The string trimmer of claim 1 , wherein the handle includes a trigger to control power to the motor to operate the motor in a normal mode where no line is paid out, and the controller comprises a switch to brake the motor and actuate the line pay-out mechanism.

4 . The string trimmer of claim 3 , wherein the controller is positioned on the handle in close proximity to the trigger so that a user can control both the trigger and controller with one hand.

5 . The string trimmer of claim 3 , wherein the switch is a momentary switch.

6 . The string trimmer of claim 1 , wherein the electric motor is a DC electric motor.

7 . The string trimmer of claim 3 , wherein the line pay-out mechanism includes a pivot arm with a weighted section and a control peg, and a corresponding control groove, the control peg positioned in the control groove to control rotation of the spool relative to the output member;
wherein a first moment is generated by the inertial forces associated with the trimming line, a second moment is generated by the inertial force of the weighted section, and a third moment generated by the braking of the motor; wherein the second moment alone is never sufficient to actuate the line pay-out mechanism; and wherein the third moment combines with the second moment to actuate the line pay-out mechanism.

8 . The string trimmer of claim 7 , wherein the pivot arm is positioned on one of the spool housing or a cap to the spool housing, and the control grooves is located on the spool.

9 . A string trimmer comprising:
an electric motor; a rotatable output member driven by the electric motor; a handle coupled to the electric motor; a spool assembly that is adapted to hold a trimming line such that the trimming line has one or more line segments that extend from the spool assembly, the spool assembly having a spool housing, a cap, a spool and a line pay-out mechanism, the spool being driven by the output member and configured such that the trimming line is wound thereon, the line pay-out mechanism being configured to control rotation of the spool relative to the output member to pay-out the trimming line from the spool in response to a difference between a first moment and a second moment, the first moment being generated by inertia of the one or more line segments, the second moment being generated by inertia of a reference weight and opposing the first moment; and a controller coupled to the electric motor and configured to electronically control the electric motor in a line pay-out mode that generates a third moment that opposes the first moment; the second moment alone never being capable of initiating the line pay-out mechanism; and the user actuating the controller to produce the third moment, the second and third moment combining to initiate the line pay-out mechanism.

10 . The string trimmer of claim 9 wherein:
the handle includes a trigger to control power to the motor, and the controller comprises a switch that brakes the motor to actuate the line pay-out mechanism; and
the controller is positioned on the handle in close proximity to the trigger so that a user can control both the trigger and controller with one hand.

11 . The string trimmer of claim 10 , wherein the electric motor is housed in a powerhead assembly.

12 . The string trimmer of claim 10 , wherein the controller shorts the motor to provide the braking effect.

13 . The string trimmer of claim 10 , wherein the controller is a DPDT switch which urges the motor in a reverse direction to provide the braking effect.

14 . The string trimmer of claim 10 , wherein the switch is a momentary switch.

15 . A method for operating a string trimmer comprising:
providing a string trimmer with an electric motor, an output member driven by the electric motor and a spool assembly, the spool assembly having a spool and a line pay-out mechanism, the spool having a cavity onto which a trimmer line is wound, the line pay-out mechanism being operable in a pay-out mode to permit the spool to rotate relative to the output member to pay-out trimmer line from the spool; providing a trigger on a handle of the string trimmer to provide power to the motor; providing a controller to effectuate a braking effect on the motor, wherein the braking effect actuates the pay-out mode; actuating the trigger to operate the motor in a trimming mode in which the electric motor operates in a first rotational direction to drive the output member, wherein inertial forces acting on the line pay-out mechanism prevent relative movement of the spool relative to the output member so that the trimming line is not paid-out from the spool assembly; and actuating the controller to pay out additional line, wherein the braking of the motor generates inertial forces that actuate the line pay-out mechanism extend trimmer line from the spool assembly.

16 . The method of claim 15 , wherein actuating the controller only momentarily brakes the motor, and the motor resumes trimming mode.

Assignees

• Black & Decker Inc

Inventors

• Sergyeyenko Oleksiy P
• Poole Brian

Classifications

• A01D34/4163 Primary

  by triggered line feedout, e.g. bump-feeding · CPC title

• A01D34/4162 Primary

  automatically · CPC title